/Engine/Source/Editor/Experimental/EditorInteractiveToolsFramework/Public/EdModeInteractiveToolsContext.h
Configure whether Transform Gizmos created by the ITF (eg CombinedTransformGizmo) should, when in World coordinate system, snap to an Absolute world-aligned grid, or snap Relative to the initial position of any particular gizmo transform. Relative is the default and is also the behavior of the standard UE Gizmo.
void SetAbsoluteWorldSnappingEnabled ( bool bEnabled )